1. Field of the Invention
The invention is based on a high-pressure pump, in particular for a fuel injection apparatus of an internal combustion engine.
2. Description of the Prior Art
A high-pressure pump of this kind is known from DE 102004027825 A1. This high-pressure pump has at least one pump element equipped with a pump piston that is driven into a stroke motion and delimits a pump working chamber. During the suction stroke of the pump piston, fuel is drawn from a fuel inlet via an inlet valve and during the delivery stroke of the pump piston, fuel is displaced from the pump working chamber via an outlet valve into a high-pressure region, for example a reservoir. The outlet valve has a valve member at least approximately in the form of a ball, a part of whose upper surface, functioning as a sealing surface, cooperates with a valve seat situated in a valve housing. In the open state when the sealing surface of the valve member is lifted away from the valve seat, the valve member opens a first flow cross section between the valve member and the valve housing. Downstream of the sealing surface, a second flow cross section is formed between the valve member and the valve housing. The outlet valve is embodied so that in the open state of the valve, the second flow cross section between the valve member and the valve housing is smaller than the first flow cross section situated in the vicinity of the sealing surface of the valve member. As a result of this, there is a lower flow speed and therefore a higher static pressure in the region of the sealing surface of the valve member than in the region of the second flow cross section. This improves the flow through the valve since the valve member opens in a stable fashion. Due to the hydraulic forces produced, however, the outlet valve can have a tendency to vibrate in some circumstances so that the outlet valve does not remain open in a stable fashion but instead opens and closes several times, interfering with the operating behavior of the high-pressure pump and causing a significant amount of strain on the high-pressure pump due to pressure peaks that occur in the pump working chamber when the outlet valve is closed. This also leads to a large amount of wear on the valve member and/or the valve seat. Moreover, the valve member can also execute movements perpendicular to its stroke direction, causing the valve member to strike the valve seat from different directions during the closing of the valve, which likewise leads to a large amount of wear.